Influence of trees on soil fertility and microbial activity Matobo, Zimbabwe
1992
Campbell, B. M. | King,F. J. | Mawanza, M. | Mhlanga, L | Piearce, G. D. | Gumbo, D. J.
An investigation into the influence of trees on soil fertility was conducted in an area of semi-arid tropical savcanna on contrasting soil types: dystrophic savanna soils (sandy soils)and eutrophic savanna soils (fine-textured soils). The study adds further support to the growing literature showing that trees have a positive influence on soild fertility. It is argued that the primary mechanism by which soil fertility is improved is through increased litter and soild organic matter compartments under trees. Orbanic matter provides much of the exchange capacity of surface soil and improves soil structure. Soil organic matter is also strongly correlated with biological activity. The influence of trees on cation levelsis greater on sandy soils that fine-textured soild because the exchange capacity of fine-textured soils is determined largely by soil texture whereas organic matter is the prime determinant of exchange capacity in sandy soils. The present study demonstrates that fertility improvementunder trees is not at the expense of fertility decline in the surface soils of the zone around the tree. Leaf quality, as reflected simply in leaf C:N ratio, influences decomposition rates but the activities of termites probably confound any simple relationship. Litter quality of tree species is important in determining levels of soil organic matter under canopies, with higher levels under species with lower leaf quality and hence more recalcitrant litter.
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